AVR32 uc3b Tx empty interrupt not working - c

Question

I am currently working on RS485 usart interrupts on AT32UCB1258 custom board and struggling with txempty interrupt.
Basically, I want to disable tx after 5 bytes have been sent.
My rx interrupt (receive command from master board) and tx ready interrupts are firing correctly, however, tx empty interrupt is not firing at all.
I am checking channel status register to distinguish which interrupt to be fired in the USART2 interrupt handler.
Any help is greatly appreciated. Thanks in advance!
//***********************USART INT HANDLER***************************************
__attribute__((__interrupt__)) static void rs485Interrupt(void)
{
if(AVR32_USART2.CSR.rxrdy)
{
gpio_set_pin_low(AVR32_PIN_PA08);
AVR32_USART2.IDR.txrdy = 1;
AVR32_USART2.IDR.txempty = 1;
rs485RxInterrupt();
}
else if(AVR32_USART2.CSR.txrdy)
{
AVR32_USART2.IDR.rxrdy = 1;
AVR32_USART2.IDR.txempty = 1;
rs485TxInterrupt();
}
else if(AVR32_USART2.CSR.txempty)
{
gpio_set_pin_low(AVR32_PIN_PA06);
rs485TxEmpty();
}
}
//**********************************************************************************
// this function is in main, and calls txrdy interrupt if data is available to send
static void rs485_write(void)
{
gpio_set_pin_high(AVR32_PIN_PA10);
txBuf[0] = ATEAddress;
AVR32_USART2.THR.txchr = txBuf[0];
tx_outctr = 1;
txLength = 5;
//txempty_flag = false;
txBuf[1] = peaks[loop][0];
txBuf[2] = peaks[loop][1];
txBuf[3] = peaks[loop][2];
txBuf[4] = peaks[loop][3];
AVR32_USART2.IER.txrdy = 1;
}
//************************TX INTERRUPT ROUTINE******************************************
static void rs485TxInterrupt(void)
{
//gpio_set_pin_low(AVR32_PIN_PA06);
for(tx_outctr=1; tx_outctr<=5; tx_outctr++)
{
//AVR32_USART2.THR.txchr = 0x01;
AVR32_USART2.THR.txchr = txBuf[tx_outctr];
//usart_write_char(&AVR32_USART2,(int)txBuf[tx_outctr]);
if (tx_outctr == 5)
{
// if 5btyes are sent, disable tx by causing txempty interrupt
AVR32_USART2.IDR.txrdy = 1;
AVR32_USART2.IER.txempty = 1;
txempty_flag = true;
}
}
//gpio_set_pin_low(AVR32_PIN_PA08);
}
//**********************************************************************************
Currently, watching gpio_pin06 going low if there is txempty interrupt, but never going to that stage.
I think usart initilisations, gpio enabling modules and interrupt registerations are correctly set since other interrupts are firing correctly.